Fix PHP 8.1 "strlen(null)" exception which blocks rendering Upload SSH Public…


Fix PHP 8.1 "strlen(null)" exception which blocks rendering Upload SSH Public key settings dialog

strlen() was used in Phabricator to check if a generic value is a non-empty string.
This behavior is deprecated since PHP 8.1. Phorge adopts phutil_nonempty_string() as a replacement.

Note: this may highlight other absurd input values that might be worth correcting
instead of just ignoring. If phutil_nonempty_string() throws an exception in your
instance, report it to Phorge to evaluate and fix that specific corner case.

Closes T15311

Test Plan:
Applied this change (on top of D25144, D25145, D25146, D25147, D25151,
D25152, D25153) and Upload SSH Public key dialog rendered in web browser.

Reviewers: O1 Blessed Committers, valerio.bozzolan

Reviewed By: O1 Blessed Committers, valerio.bozzolan

Subscribers: speck, tobiaswiese, valerio.bozzolan, Matthew, Cigaryno

Maniphest Tasks: T15311

Differential Revision: https://we.phorge.it/D25161